A DC9 CARGO CREW OVERSHOOTS THEIR ASSIGNED ALT BY 1000 FT. CREW FAILED TO SET THEIR ALTIMETER TO THE CORRECT LCL SETTING; MISREADING AND MISSETTING THEM 1000 FT LOW OR 1 INCH OFF NEAR DAY; OH.

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ON CLBOUT FROM ILN; ATC RPTED A 1000 FT ALT DIFFERENCE BTWN THE RADAR AND XPONDER/PLT CHK-IN ALTS. THE CTLR ASKED US TO VERIFY THE ALTIMETER SETTING. WHILE TROUBLESHOOTING; THE OPPOSITE ALTIMETER WAS SELECTED AS THE 'RPTING' ALTIMETER FOR THE XPONDER. IT WAS THEN DISCOVERED BOTH ALTIMETERS HAD BEEN SEPARATELY SET TO A SETTING WHICH WAS OFF BY 1 INCH OR 1000 FT. MAINT RECORDS SHOW THE PITOT STATIC SYS HAD BEEN PREVIOUSLY WORKED ON AND SET TO SEA LEVEL ELEVATION. ON PREFLT; BOTH PLTS SEPARATELY MADE THE SAME MISTAKE OF ADJUSTING THE ALTIMETER SETTING BY A FEW DIGITS RATHER THAN AN INCH AND A FEW DIGITS. SUPPLEMENTAL INFO FROM ACN 471867: SHORTLY THEREAFTER; I TOOK YET ANOTHER LOOK AT THE ALTIMETER SETTING AND FINALLY NOTICED THAT I HAD 28.92 SET ON MY ALTIMETER; AND THE FO HAD MADE THE SAME MISTAKE ON HIS SIDE AND ON THE STANDBY UNIT. IN OUR COMPLACENCY; WE MADE THE SMALL ADJUSTMENT TO THE ALTIMETERS THAT IS NORMALLY REQUIRED AND WE BOTH SAW WHAT WE EXPECTED TO SEE. IT WOULD ALSO BE A GREAT HELP IF THE BACKGND COLOR BEHIND THEM WOULD BE OF A DIFFERENT COLOR AT UNUSUALLY HIGH AND LOW BAROMETRIC SETTINGS.